Oral disposition index predicts the development of future diabetes above and beyond fasting and 2-h glucose levels.
OBJECTIVE
We sought to determine whether an oral disposition index (DI(O)) predicts the development of diabetes over a 10-year period. First, we assessed the validity of the DI(O) by demonstrating that a hyperbolic relationship exists between oral indexes of insulin sensitivity and beta-cell function.


METHODS
A total of 613 Japanese-American subjects (322 men and 291 women) underwent a 75-g oral glucose tolerance test (OGTT) at baseline, 5 years, and 10 years. Insulin sensitivity was estimated as 1/fasting insulin or homeostasis model assessment of insulin sensitivity (HOMA-S). Insulin response was estimated as the change in insulin divided by change in glucose from 0 to 30 min (DeltaI(0-30)/DeltaG(0-30)).


RESULTS
DeltaI(0-30)/DeltaG(0-30) demonstrated a curvilinear relationship with 1/fasting insulin and HOMA-S with a left and downward shift as glucose tolerance deteriorated. The confidence limits for the slope of the log(e)-transformed estimates included -1 for DeltaI(0-30)/DeltaG(0-30) versus 1/fasting insulin for all glucose tolerance groups, consistent with a hyperbolic relationship. When HOMA-S was used as the insulin sensitivity measure, the confidence limits for the slope included -1 only for subjects with normal glucose tolerance (NGT) or impaired fasting glucose (IFG)/impaired glucose tolerance (IGT) but not diabetes. On the basis of this hyperbolic relationship, the product of DeltaI(0-30)/DeltaG(0-30) and 1/fasting insulin was calculated (DI(O)) and decreased from NGT to IFG/IGT to diabetes (P < 0.001). Among nondiabetic subjects at baseline, baseline DI(O) predicted cumulative diabetes at 10 years (P < 0.001) independent of age, sex, BMI, family history of diabetes, and baseline fasting and 2-h glucose concentrations.


CONCLUSIONS
The DI(O) provides a measure of beta-cell function adjusted for insulin sensitivity and is predictive of development of diabetes over 10 years.
Utzschneider
Kristina M
KM
Division of Metabolism, Endocrinology and Nutrition, Department of Medicine, Veterans Affairs Puget Sound Health Care System, Seattle, Washington, USA. kutzschn@u.washington.edu
Prigeon
Ronald L
RL
Faulenbach
Mirjam V
MV
Tong
Jenny
J
Carr
Darcy B
DB
Boyko
Edward J
EJ
Leonetti
Donna L
DL
McNeely
Marguerite J
MJ
Fujimoto
Wilfred Y
WY
Kahn
Steven E
SE
D001786:Blood Glucose / Q000378:metabolism*; D003920:Diabetes Mellitus / Q000097:blood / Q000453:epidemiology*; D005215:Fasting; D005246:Feedback; D005500:Follow-Up Studies; D005951:Glucose Tolerance Test / Q000379:methods*; D006801:Humans; D006943:Hyperglycemia / Q000453:epidemiology; D007328:Insulin / Q000502:physiology*; D007333:Insulin Resistance; D050417:Insulin-Secreting Cells / Q000378:metabolism / Q000502:physiology; D011237:Predictive Value of Tests; D012044:Regression Analysis; D015203:Reproducibility of Results; D013997:Time Factors
D001786:Blood Glucose; D007328:Insulin